Single-particle versus pair condensation of hard-core bosons with correlated hopping

Schmidt, K. P.; Dorier, J.; Laeuchli, A.; Mila, F.

Single-particle versus pair condensation of hard-core bosons with correlated hopping

Authors

Description

We investigate the consequences of correlated hopping on the ground state properties of hard-core bosons on a square lattice as revealed by extensive exact diagonalizations and quantum Monte Carlo simulations. While for non interacting hard-core bosons the effective attraction induced by the correlated hopping leads to phase separation at low density, we show that a modest nearest-neighbor repulsion suppresses phase separation, leading to a remarkable low-density pairing phase with no single particle Bose-Einstein condensation but long-range two-particle correlations, signaling a condensation of pairs. We also explain why the unusual properties of the pairing phase are a real challenge for standard one-worm quantum Monte Carlo simulations.
8 pages, 7 figures